/*
 *	qsort_arg.c: qsort with a passthrough "void *" argument
 *
 *	Modifications from vanilla NetBSD source:
 *	  Add do ... while() macro fix
 *	  Remove __inline, _DIAGASSERTs, __P
 *	  Remove ill-considered "swap_cnt" switch to insertion sort,
 *	  in favor of a simple check for presorted input.
 *
 *	CAUTION: if you change this file, see also qsort.c, gen_qsort_tuple.pl
 *
 *	src/port/qsort_arg.c
 */

/*	$NetBSD: qsort.c,v 1.13 2003/08/07 16:43:42 agc Exp $	*/

/*-
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	  notice, this list of conditions and the following disclaimer in the
 *	  documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *	  may be used to endorse or promote products derived from this software
 *	  without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.	IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include "c.h"

static char* med3(char* a, char* b, char* c, qsort_arg_comparator cmp, void* arg);
static void swapfunc(char*, char*, size_t, int);

/*
 * Qsort routine based on J. L. Bentley and M. D. McIlroy,
 * "Engineering a sort function",
 * Software--Practice and Experience 23 (1993) 1249-1265.
 * We have modified their original by adding a check for already-sorted input,
 * which seems to be a win per discussions on pgsql-hackers around 2006-03-21.
 */
#define swapcode(TYPE, parmi, parmj, n)   \
    do {                                  \
        size_t i = (n) / sizeof(TYPE);    \
        TYPE* pi = (TYPE*)(void*)(parmi); \
        TYPE* pj = (TYPE*)(void*)(parmj); \
        do {                              \
            TYPE t = *pi;                 \
            *pi++ = *pj;                  \
            *pj++ = t;                    \
        } while (--i > 0);                \
    } while (0)

#define SWAPINIT(a, es) \
    swaptype = ((char*)(a) - (char*)0) % sizeof(long) || (es) % sizeof(long) ? 2 : ((es) == sizeof(long) ? 0 : 1);

static void swapfunc(char* a, char* b, size_t n, int swaptype)
{
    if (swaptype <= 1) {
        swapcode(long, a, b, n);
    } else {
        swapcode(char, a, b, n);
    }
}

#define swap(a, b)                               \
    if (swaptype == 0) {                         \
        long t = *(long*)(void*)(a);             \
        *(long*)(void*)(a) = *(long*)(void*)(b); \
        *(long*)(void*)(b) = t;                  \
    } else                                       \
        swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n) \
    if ((n) > 0)         \
    swapfunc((a), (b), (size_t)(n), swaptype)

#define returnifzero(a)   \
    if (a == 0) {         \
        return;           \
    }                     \

static char* med3(char* a, char* b, char* c, qsort_arg_comparator cmp, void* arg)
{
    return (cmp(a, b, arg) < 0) ? ((cmp(b, c, arg) < 0) ? b : ((cmp(a, c, arg) < 0) ? c : a))
                              : ((cmp(b, c, arg) > 0) ? b : ((cmp(a, c, arg) < 0) ? a : c));
}

void qsort_arg(void* a, size_t n, size_t es, qsort_arg_comparator cmp, void* arg)
{
    char *pa = NULL, *pb = NULL, *pc = NULL, *pd = NULL, *pl = NULL, *pm = NULL, *pn = NULL;
    int d, r, swaptype, presorted;

    returnifzero(es);

loop:
    SWAPINIT(a, es);
    if (n < 7) {
        for (pm = (char*)a + es; pm < (char*)a + n * es; pm += es)
            for (pl = pm; pl > (char*)a && cmp(pl - es, pl, arg) > 0; pl -= es)
                swap(pl, pl - es);
        return;
    }
    presorted = 1;
    for (pm = (char*)a + es; pm < (char*)a + n * es; pm += es) {
        if (cmp(pm - es, pm, arg) > 0) {
            presorted = 0;
            break;
        }
    }
    if (presorted) {
        return;
    }
    pm = (char*)a + (n / 2) * es;
    if (n > 7) {
        pl = (char*)a;
        pn = (char*)a + (n - 1) * es;
        if (n > 40) {
            d = (n / 8) * es;
            pl = med3(pl, pl + d, pl + 2 * d, cmp, arg);
            pm = med3(pm - d, pm, pm + d, cmp, arg);
            pn = med3(pn - 2 * d, pn - d, pn, cmp, arg);
        }
        pm = med3(pl, pm, pn, cmp, arg);
    }
    swap((char*)a, pm);
    pa = pb = (char*)a + es;
    pc = pd = (char*)a + (n - 1) * es;
    for (;;) {
        while (pb <= pc && (r = cmp(pb, a, arg)) <= 0) {
            if (r == 0) {
                swap(pa, pb);
                pa += es;
            }
            pb += es;
        }
        while (pb <= pc && (r = cmp(pc, a, arg)) >= 0) {
            if (r == 0) {
                swap(pc, pd);
                pd -= es;
            }
            pc -= es;
        }
        if (pb > pc) {
            break;
        }
        swap(pb, pc);
        pb += es;
        pc -= es;
    }
    pn = (char*)a + n * es;
    r = Min(pa - (char*)a, pb - pa);
    vecswap((char*)a, pb - r, r);
    r = Min((size_t)(pd - pc), (size_t)(pn - pd - es));
    vecswap(pb, pn - r, r);
    if ((size_t)(r = pb - pa) > es)
        qsort_arg(a, r / es, es, cmp, arg);
    if ((size_t)(r = pd - pc) > es) {
        /* Iterate rather than recurse to save stack space */
        a = pn - r;
        n = r / es;
        goto loop;
    }
}
